Device and method for determining media characteristics and container characteristics

ABSTRACT

A fill-level measuring device includes a self-learn device that is able to automatically determine the length of the dome shaft of the container. To this effect the self-learn device uses a multiple echo classified as such by a multiple-echo detection device. In this manner the result of fill level measuring may be improved.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of EP PatentApplication Serial No. EP 11 167 946.0 filed 27 May 2011 and U.S. PatentApplication Ser. No. 61/490,745 filed 27 May 2011, the disclosure ofboth applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to fill level measuring. In particular,the invention relates to a fill-level measuring device for determiningthe position of a fill level of a feed material and/or of an interfacebetween two feed materials for determining media characteristics andcontainer characteristics when measuring fill levels of any kind, to acorresponding method, to a program element and to a computer-readablemedium.

BACKGROUND INFORMATION

In fill level sensors operating according to the FMCW or pulse-transittime method, electromagnetic or acoustic waves are emitted in thedirection of a feed material surface. Following this, a sensor recordsthe echo signals reflected by the feed material, by the objects builtinto the container, and by the container itself, and from this derivesthe position of a surface of at least one of the feed materialscontained in the container.

With the use of acoustic or optical waves the signal generated by thefill-level measuring device generally propagates freely in the directionof the feed material surface to be measured. In devices that use radarwaves for measuring the feed material surface, both free propagation inthe direction of the medium to be measured can be considered, andpropagation in the interior of a waveguide that guides the radar wavesfrom the fill-level measuring device to the medium. In devices operatingaccording to the principle of the guided microwave the high-frequencysignals are guided along a waveguide to the medium.

At the surface of the medium or fill level to be measured, some of thearriving signals are reflected and after a corresponding transit timereturn to the fill-level measuring device. The non-reflected signalcomponents penetrate the medium and in the medium continue to propagate,corresponding to the physical characteristics of the medium, in thedirection of the container bottom. At the container bottom thesesignals, too, are reflected and after passing through the medium and theoverlaid atmosphere return to the fill-level measuring device.

The fill-level measuring device receives the signals, which have beenreflected at different positions, and from them determines the distanceto the feed material according to known methods. The determined distanceto the feed material is made available externally. Such provision can beimplemented in an analog form (4 . . . 20 mA interface) or in a digitalform (fieldbus).

All the methods share a common feature in that on its way from thefill-level measuring device to the feed material surface the signal usedfor measuring is normally in the region of influence of a furthermedium, which hereinafter is referred to as the overlay medium. Thisoverlay medium is situated between the fill-level measuring device andthe surface of the medium to be measured, and is generally representedby a liquid or by a gaseous atmosphere.

In a predominant number of applications there is air above the medium tobe measured. Since the propagation of electromagnetic waves in airdiffers only insignificantly from that in a vacuum, there is no need tocarry out any special corrections of the signals that are reflected,through the air back to the fill-level measuring device, by the feedmaterial, by the objects built into the container, and by the containeritself.

Furthermore, however, in process containers of the chemical industrymany types of chemical gases and gas mixtures can occur as overlaymedia. Depending on the physical characteristics of these gases or gasmixtures, the propagation characteristics of electromagnetic waves arechanged when compared to propagation in a vacuum or in air.

Known attempts at determining media characteristics and containercharacteristics are often associated with significant weaknesses.

SUMMARY OF THE INVENTION

It would be desirable to have a robust method and a device fordetermining media characteristics and container characteristics.Furthermore, it would be desirable to have a method and a device forautomatically determining the parameters when taking interfacemeasurements.

Stated are a fill-level measuring device for determining the position ofa fill level and/or of an interface between two feed materials, whichare, for example, contained in a container; a method, a program elementand a computer-readable medium according to the characteristics of theindependent claims. Developments to the invention are stated in thesubordinate claims as well as in the following description.

It should be pointed out that hereinafter with regard to the fill-levelmeasuring device the above-mentioned characteristics may also beimplemented as method-related steps in the method, and vice versa.

According to a first aspect of the invention, a fill-level measuringdevice for determining the position of a fill level of a feed materialwhich is, for example, contained in a container, and/or of an interfacebetween two feed materials is stated. The fill-level measuring devicecomprises an echo-curve acquisition device for acquiring one or severalecho curves, an echo identification device for evaluating the at leastone echo curve, a multiple-echo detection device for evaluating the atleast one echo curve, a multiple-echo detection device for classifyingone or several echoes of a multiple reflection from a feed materialsurface and/or from a container bottom of the container as a multipleecho, as well as a device, which may have “self-learning” ability andmay for this reason, also be denoted as “self-learning”, and which isdesigned for automatically determining the length of the dome shaft ofthe container with the use of the multiple echo classified by themultiple-echo detection device.

According to a further aspect of the invention the fill-level measuringdevice may comprise a position determination device. The echoidentification device may be designed for identifying several echoes inthe echo curve, and the multiple-echo detection device can be designedfor classifying at least two of the several echoes as multiple echoes.Furthermore, the position determination device can be designed fordetermining positions of the at least two multiple echoes, and theself-learn device can be designed for using the positions of the atleast two multiple echoes for determining the length of the dome shaft.

According to a further aspect of the invention, the self-learn devicefor use of the orders of the at least two multiple echoes may bedesigned for determining the length of the dome shaft.

According to a further aspect of the invention, the echo identificationdevice may be designed for identifying several echoes in the echo curve,and the multiple-echo detection device can be designed for classifyingtwo or more echoes as multiple echoes.

Furthermore, the fill-level measuring device may comprise a speeddetermination device for determining a first speed vector of a firstmultiple echo of the echoes classified as multiple echoes, and fordetermining a second speed vector of a second multiple echo of theclassified multiple echoes. The self-learn device is designed fordetermining an intersection of at least two of the determined speedvectors for determining the length of the dome shaft.

According to a further aspect of the invention, a method for determiningthe position of a fill level of a feed material in a container and/or ofan interface between two feed materials in a container is stated.Acquisition of at least one echo curve takes place, which echo curve issubsequently evaluated. Furthermore, classification of at least one echoof a multiple reflection from a feed material surface of the feedmaterial and/or from a container bottom of the container takes place asa multiple echo. Furthermore, automatic determination of a length of thedome shaft of the container takes place with the use of the multipleechoes classified by the multiple-echo detection device.

According to a further aspect of the invention, a program element isstated which, when executed on a processor of a fill-level measuringdevice, instructs the processor to carry out the steps described aboveand/or below.

Furthermore, a computer-readable medium for storing a program element isstated which, when executed on a processor of a fill-level measuringdevice, instructs the processor to carry out the steps described aboveand/or stated below.

The program element (referred to as the “computer program element”) canform part of software that is stored on a processor of the fill-levelmeasuring device. In this arrangement the processor can also be thesubject of the invention. Furthermore, this aspect of the inventioncomprises a computer program element that from the very beginning usesthe invention, as well as a computer program element, which by way of anupdate causes an existing program to use the inventions.

It should be pointed out that the term “feed material echo” equates to amultiple echo of the order of zero of the feed material reflection.

Furthermore, it should be pointed out that the term “bottom echo”equates to a multiple echo of the order of zero of the bottomreflection.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a fill-level measuring device that operates according to atransit time method.

FIG. 2 shows method-related steps for determining the fill levelaccording to a transit time method.

FIG. 3 shows conditions where the container basin is not straight.

FIG. 4 shows an example of fill level measuring with multiple echoes.

FIG. 5 shows an example of fill level measuring in a dome shaft.

FIG. 6 shows an example of fill level measuring without a containercover.

FIG. 7 shows a fill-level measuring device according to an exemplaryembodiment of the invention.

FIG. 8 shows measuring cycles with a fill-level measuring deviceaccording to an exemplary embodiment of the invention.

FIG. 9 shows a method for determining a length of the dome shaftaccording to an exemplary embodiment of the invention.

FIG. 10 shows a method for determining the container height according toan exemplary embodiment of the invention.

FIG. 11 shows a fill-level measuring device for interface measuringaccording to an exemplary embodiment of the invention.

FIG. 12 shows interface measuring with a constant distance to aninterface according to an exemplary embodiment of the invention.

FIG. 13 shows interface measuring with a constant distance to a feedmaterial surface according to an exemplary embodiment of the invention.

FIG. 14 shows interface measuring with a constant thickness of the uppermedium according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION

The illustrations in the figures are diagrammatic and not to scale.

If in the following description of the figures in different figures thesame reference characters are used, they designate identical or similarelements. However, identical or similar elements can also be designatedby different reference characters.

It should be pointed out that the term “feed material echo” equates to amultiple echo of the order of zero of the feed material reflection.

Furthermore, it should be pointed out that the term “bottom echo”equates to a multiple echo of the order of zero of the reflection of thebottom of the container.

The explanations below concentrate on considering thefrequently-occurring application case of a single medium or feedmaterial to be measured in a container. The technical teaching describedbelow can be transposed to the application case of two or severaldifferent media or feed materials in a container. In the context ofinterface measuring, the position of a feed material surface may, inparticular, also be the position of an interface between two differentmedia or feed materials, which position is identical to the position ofthe feed material surface of the lower of the two feed materials ormedia in a container for interface measuring.

In devices for fill level measuring, various methods can be usedaccording to which the position of a feed material surface in acontainer can be determined.

FIG. 1 shows an arrangement for fill level measuring. The container 100contains a liquid 106 up to a fill height d_(B)-d_(L). The space 107above the liquid contains, for example, air. In the present example theliquid is covered by air as an overlay medium.

By means of a high-frequency device 102 the fill-level measuring device101 generates an electromagnetic pulse 103 and couples it into asuitable antenna 104, whereupon this pulse propagates almost at thespeed of light in the direction of the feed material surface 105 to bemeasured. The precise speed within the overlay medium results from:

$c_{L} = \frac{c_{0}}{\sqrt{ɛ_{L} \cdot \mu_{L}}}$

wherein c₀ denotes the speed of light in a vacuum, ε_(L) thepermittivity value of the overlay medium, and μ_(L) the permeabilityvalue of the overlay medium.

The feed material surface 105 reflects part of the incoming signalenergy, whereupon the reflected signal component propagates back to thefill-level measuring device 101. The non-reflected signal componentpenetrates the liquid 106, and within it propagates at a greatly reducedspeed in the direction of the container bottom. The speed c_(M) of theelectromagnetic wave 103 within the liquid 106 is determined by thematerials characteristics of the liquid 106:

$c_{M} = \frac{c_{0}}{\sqrt{ɛ_{M} \cdot \mu_{M}}}$

wherein c₀ denotes the speed of light in a vacuum, ε_(M) thepermittivity value of the liquid, and the permeability value of theliquid. At the bottom 108 of the container 109 the remaining signalcomponent is also reflected and, after a corresponding transit time,returns to the fill-level measuring device 101. In the fill-levelmeasuring device the incoming signals are processed by means of thehigh-frequency device 102, and are preferably transformed to alower-frequency intermediate frequency range. By means of ananalog/digital converter unit 110, the analog echo curves, which areprovided by the high-frequency device 102, are digitized and madeavailable to an evaluation device 111.

The above-mentioned components, which are used to provide a digitizedecho curve, in other words in particular the high-frequency device 102and the analog/digital converter unit 110, may, as an example, define anecho-curve acquisition device.

The evaluation device 111 analyzes the digitized echo curve and, on thebasis of the echoes contained therein determines according to knownmethods that echo that was generated by the reflection from the feedmaterial surface 105. Furthermore, the evaluation device determines theprecise electrical distance to this echo. Furthermore, the determinedelectrical distance to the echo is corrected in such a manner thatinfluences of the overlay medium 107 on the propagation of theelectromagnetic waves are compensated for. The compensated distance tothe feed material, which distance has been calculated in this manner, isconveyed to an output device 112, which further processes the determinedvalue according to user specifications, for example by means oflinearization, offset correction, conversion to a fill heightd_(B)-d_(L). The processed measured value is provided to the outside atan external communication interface 113. In this context any of theestablished interfaces can be used, in particular 4 . . . 20 mA currentinterfaces, industrial fieldbuses such as HART, Profibus, FF, orcomputer interfaces such as RS232, RS485, USB, Ethernet, FireWire.

FIG. 2 again illustrates in detail important steps that in the contextof echo signal processing can be applied in the evaluation device 111for compensating the influences of various media.

Curve 201 in the first instance shows the echo curve 204 acquired by theanalog/digital converter unit 110 over time. The echo curve in the firstinstance contains the component of the transmitting pulse 205 reflectedwithin the antenna. A short time later at the point in time t_(L) afirst echo 206 is acquired, which has been caused by the reflection ofsignal components from the boundary surface 105 or surface 105 of themedium 106 in the container. A further echo 207 arises as the firstmultiple echo of the feed material echo 206; it is acquired at the pointin time t_(ML). After the signal components penetrating the medium 106have moved through the feed material 106, they are reflected from thecontainer bottom 108 and generate a further echo 208 within the echocurve 204. This bottom echo 208 is acquired at the point in time t_(B).Furthermore, at the point in time t_(MB) a multiple echo 209 of thebottom echo may be acquired.

In a first process step the time-dependent curve 201 is transformed to adistance-dependent curve 202. During this transformation it is assumedthat the acquired curve has formed exclusively as a result ofpropagation in a vacuum. The ordinate of the diagram 201 is converted toa distance axis by multiplication with the speed of light in a vacuum.Furthermore, by applying an offset a situation is achieved in which theecho 205 caused by the antenna 104 obtains a distance value of 0 m.Furthermore, the distance values are multiplied by the factor of 0.5 tocompensate for the double path to the feed material surface and back.

The second diagram 202 shows the echo curve as a function of theelectrical distance D. The electrical distance corresponds to half thedistance covered by an electromagnetic wave in a vacuum in a definedperiod of time. The electrical distance does not take into account anyinfluences of a medium, which influences may result in a slowdown in thepropagation of the electromagnetic waves. Curve 202 thus represents anon-compensated-for echo curve which is, however, related to locations.

In this document the electrical distances are always designated by theupper case letter D, whereas physical distances, which can be directlymeasured on the container, are designated by the lower case letter d.

Furthermore, it may be possible to fully compensate the echo curve 210.The third diagram 203 shows a fully-compensated echo curve 211. In orderto obtain a diagram of the echoes over the physical distance, in thepresent case the influence of the overlay medium 107 in the regionbetween the locations 0 and D_(L) (curve 202) need to be taken intoaccount. The electrical distance values of the abscissa between 0 andD_(L) need to be converted to physical distance values according to thefollowing correlation:

$d_{i} = \frac{D_{i}}{\sqrt{ɛ_{L} \cdot \mu_{L}}}$

Since ε_(Luft)ε_(L) and μ_(Luft)μ_(L) for air in good approximationcorrespond to the value 1, no correction needs to take place in relationto this section in the present example. However, the electrical distancevalues of the abscissa greater than or equal to D_(L) need to beconverted to physical distance values according to the followingcorrelation:

$d_{i} = {d_{L} + \frac{\left( {D_{i} - D_{L}} \right)}{\sqrt{ɛ_{M} \cdot \mu_{M}}}}$

The third diagram 203 finally shows the corrected curve. Both thedistance to the echo 206 of the feed material surface 105 and thedistance to the echo 208 generated by the container bottom 108 agreewith the distances that can be measured on the container 109. Thedistance to the multiple echo 207 of the feed material surface cannot bemeasured directly on the container because the above compensationapplies only to direct reflections. The same applies to the multipleecho 209 of the reflection on the container bottom 108.

At this stage it should be pointed out that the conversion in curve 202,in other words determining the electrical distances of various echoes,in the context of signal processing can preferably be carried out in thedevice in relation to all the echoes. Generally-speaking, conversion ofthe echo curve to a compensated echo curve is not carried out, becausecorrection of an individual distance value to the feed material surfaceis sufficient.

FIG. 3 illustrates the use of an indirect or direct determination of theposition of the feed material surface by means of a bottom echo. Thecontainer 301 shown is almost completely full of feed material 302. Incontrast to the container 109 of FIG. 1, the fill-level measuring device101 in the container 301 of FIG. 3 may be installed so as to be in adome shaft 303. A dome shaft may be a shaft by way of which the tank canbe filled. A dome shaft may also be implemented by an access option forservice personnel, a so-called manhole. Furthermore, it may also bepossible to use a dome shaft for other purposes. In the so-called domeat the apex of the tanks, among other things the fill-level measuringdevice can be in place.

Apart from the echo 305 generated by the antenna 104, the echo curve 304acquired by the fill-level measuring device 101 comprises only onemultiple reflection ε_(ML1) 306 from the feed material surface 307 andthe bottom echo 309 generated by the container bottom 308. The echogenerated by the surface 307 of the medium cannot reliably be detectedby the acquired echo curve 304 since in the region of influence of theantenna echo 305 said echo is completely covered by said antenna echo305. The distance d_(L) to the feed material surface cannot bedetermined in a conventional manner.

The position of the feed material surface can be measured indirectly sothat the position dr, of the feed material surface can be determinedaccording to the following equation from the electrical distance D_(B)of the bottom echo:

$d_{L} = \frac{{d_{B} \cdot \sqrt{ɛ_{M} \cdot \mu_{M}}} - D_{B}}{\sqrt{ɛ_{M} \cdot \mu_{M}} - \sqrt{ɛ_{L} \cdot \mu_{L}}}$

In a multitude of practical applications, because of the high lossvalues of the signals in the medium, the bottom echo 309 in the echocurve can no longer be detected.

Furthermore, from the position of a multiple echo E_(ML1) 306 it ispossible to deduce the position d_(L) of the feed material surface:

$d_{L} = \frac{D_{{ML}\; 1} + {\sqrt{ɛ_{L} \cdot \mu_{L}} \cdot N \cdot d_{D}}}{\left( {1 + N} \right) \cdot \sqrt{ɛ_{L} \cdot \mu_{L}}}$

wherein N denotes the order of the multiple echo at the distanceD_(ML1).

Moreover, multiple echoes and bottom echoes can be detected in that thespeed values and/or the positions of several echoes of an echo curve canbe analyzed.

A knowledge of the permittivity values and permeability values of themedia contained in the container 301, as well as a knowledge of thegeometric dimensions of the container, in particular of the length ofthe dome shaft d_(D) and of the expanded container height d_(B) or ofthe container height d_(b)-d_(D), is a basic prerequisite for carryingout indirect measuring.

FIG. 4 illustrates the physical correlations that may give rise to theformation of multiple echoes.

The fill-level measuring device 401 generates an electromagnetic pulse402 according to known methods and emits this pulse 402 in the directionof the feed material surface 105 to be measured. The signal arrow 403indicates the propagation of the signal as a function of the physicaldistance over time. Part of the transmit signal is reflected from thesurface of the feed material 105 and after a corresponding transit timereturns to the fill-level measuring device. The signal path 404illustrates this propagation path. Based on the received signals, thefill-level measuring device forms an echo curve 204 which, due to thesignal paths 403 and 404, comprises a first echo E_(L) 206. A componentof the signals is reflected anew, for example from the container ceiling405 or from the fill-level measuring device 401, and propagates in thedirection of the feed material surface 105, which is indicated by thesignal arrow 406. This signal component is again reflected from the feedmaterial surface, and after a corresponding transit time returns to thefill-level measuring device 401, where it is acquired as the firstmultiple echo E_(ML1) 207 of the feed material reflection and isdepicted in the echo curve 204; signal path 407 illustrates the process.

Part of the radiated signal energy 402, which part is not reflected fromthe feed material surface 105, penetrates the medium 106 and within itcontinues to propagate 408 at reduced speed in the direction of thecontainer bottom 108. At the container bottom the signal is reflectedand after a corresponding transit time returns to the fill-levelmeasuring device. The signal paths 409 and 410 illustrate thepropagation of the signal on this path. It should be noted that thesignal propagates at different speeds in the various media, which in thesignal path diagram is evident by the different gradients of the signalpaths 409, 410. The fill-level measuring device receives the signalcomponents reflected from the container bottom and depicts them in theform of a bottom echo E_(B) 208 in the echo curve 204. Analogous to theformation of multiple echoes 207, 415 of the feed material reflection,under favorable conditions the formation of one or several multipleechoes of the bottom echo can also be observed. The signal paths 411,412, 413, 414 illustrate the formation of a first multiple echo E_(MB)209 of the bottom echo E_(B) 208, which after a corresponding transittime also forms in the echo curve 204 received by the fill levelmeasuring device.

In principle it is possible to construct higher-order multiple echoes.With regard to this the signal path diagram shows the signal paths 417and 418 that are suitable to generate a second-order multiple echoE_(ML2) 415 relative to the reflection from the feed material surface.Corresponding higher-order multiple echoes are also possible in relationto the reflection from the container bottom. The average person skilledin the art may not encounter any problems in transposing the aspects ofthe present invention, which aspects are hereinafter presented by meansof the multiple echoes of the first order, to higher-order multipleechoes. The order of a multiple echo is defined as the number ofreflections of an emitted signal from a media surface of a feed materialto be measured in the container, reduced by 1. According to thisnomenclature, the echo is identical to a multiple echo of the order of0, whereas the echo E_(ML1) is identical to a multiple echo of the firstorder.

Furthermore, mixed signal paths are also imaginable that lead to furtherechoes within the received echo curves. Thus it may, for example, bepossible for the signal, after passing along the signal path 406, topenetrate the medium and to propagate in the direction of the containerbottom. Furthermore, it may, for example, also be possible for part ofthe signal energy, after passing along the signal path 411, to bereflected from the feed material surface, and to propagate againdirectly in the direction of the fill-level measuring device. In thecontext of the present invention, mixed signal paths should not befurther considered because in practical application they are almostirrelevant. However, the average person skilled in the art may notencounter any problems in transposing the aspects of the presentinvention, which aspects are hereinafter presented by means of themultiple echoes of the first order, to mixed multiple echoes. In thepresent context mixed echoes are defined as echoes of an echo curve thatare caused by signal paths within which a signal generated by thefill-level measuring device is reflected from at least two differentboundary surfaces of at least one feed material to be measured in acontainer. The present example does not contain a mixed multiple echo.

Consideration can be less extensive with the use of a fill-levelmeasuring device in a container with a dome shaft in place. FIG. 5 showsan example of the use of the measuring device 401 according to theinvention in such a container 501. The fill-level measuring device isnot installed directly at the height of the container ceiling 502;instead, it is situated in a dome shaft 503 which, in contrast to theexample of FIG. 4, in FIG. 5 comprises a physical length of d_(D)>0. Theinstallation position of the fill-level measuring device in the domeshaft massively influences the formation of multiple echoes. The signalpath diagram 504 illustrates the formation of multiple echoes in thepresent case. The signal generated by the fill-level measuring device inthe first instance propagates through the dome shaft 503 and the actualcontainer to the surface of the medium 505. Signal path 506 illustratesthis signal path. The medium reflects the signal, whereupon said signalpropagates in the direction of the fill-level measuring device 401.Since the opening 513 of the dome shaft 503 is small in relation to thecontainer ceiling 502, only a very small part of the signal is shown asa fill level echo E_(L) 515 in the echo curve 514.

The signal paths 507 and 508 illustrate this propagation path. By farthe larger part of the signal energy is reflected from the containerceiling (signal path 509), and reaches the feed material surface again.In this manner, after the signal has passed along the signal paths 509,510, and 511, a first multiple echo E_(ML) 516 is shown in the echocurve. The interrelations presented in the context of dome shaftscorrespondingly also apply to the higher-order multiple echoes, which isindicated by the signal path 512; said interrelations also apply to themultiple echoes of the bottom reflection.

Moreover, in industrial applications there are also constellations whichwith the introduction of a negative length of the dome shaft can beprocessed in an advantageous manner. FIG. 6 shows such an applicationcase. The fill-level measuring device 401 is installed above an open-topcontainer 60, wherein the entire measuring arrangement is, for example,situated in a hall so that there may be a metallic flat roof 602 abovethe arrangement. In the course of signal processing of the fill-levelmeasuring device 401, the space between the reference plane 603 of thefill-level measuring device 401 and the hall roof 602 is taken intoaccount as a negative length of the dome shaft with a physical length ofd_(D)>0. Thus, in the context of the present invention the applicationmay comprise a dome shaft, wherein the latter may comprise a negativelength. When measuring is subsequently carried out by the fill-levelmeasuring device 401, signal paths as shown in the signal path diagram604 result. The direct reflection from the feed material surface, whichis illustrated by the signal paths 605 and 606, is shown in the echocurve as a fill level echo E_(L) 610. However, by far the greater partof the signal energy propagates as far as the hall roof 602, isreflected by the aforesaid, and after renewed reflection from the feedmaterial surface leads to the first multiple echo E_(ML) 611 within theecho curve 612. The signal propagation that results in this echo isindicated by the signal paths 607, 608 and 609.

In practical application the interrelationships described above can leadto problems when measuring the fill level, in particular in the case ofindirect measuring. The demonstrated methods for indirectly determiningthe position of a feed material according to FIG. 3 require a preciseknowledge of some container characteristics such as the container heightor the length of the dome shaft, and moreover the information relatingto the permeability values and permittivity values of the mediacontained in the container.

Apart from manual input of the required parameters by the user, variousmethods for determining the values can be used.

Many of these methods determine the permittivity of a medium from thepositions, which have been determined by measurement, of the feedmaterial reflection and of the bottom reflection. This approach isassociated with disadvantages in that it is necessary to know in advancethe height of the container and if applicable also the height of a domeshaft. Furthermore, the determination is associated with considerableinaccuracies because the individual values, which have been determinedby measurement, can become falsified by the effects of noise.

Furthermore, automated determination of the container height is onlypossible if, apart from the permittivity of the media in the container,the length of a possibly present dome shaft is also known in advance.

Attempts at determining the permittivity by means of an echo amplitudecan be unreliable in practical application, because the amplitude of anecho can be massively compromised by layers in the case of bulkmaterials, and by foam in the case of liquids.

Many attempts at determining media characteristics and containercharacteristics thus do not provide robust methods which in the contextof fill level measuring under real-life conditions would result inimprovements. Furthermore, by means of the above-mentioned methods it isnot possible to carry out automatic determination of the parameters inthe context of interface measuring.

The block diagram of FIG. 7 shows an example of a fill-level measuringdevice and a device for determining media characteristics and containercharacteristics according to an exemplary embodiment of the invention.

The fill-level measuring device 701 largely corresponds to thefill-level measuring device 101 shown in FIG. 1, but it differs from thedevices used so far by a modified evaluation device 702.

The evaluation device 702 may comprise, or consist of, an echoidentification device 7021, a tracking device 7022, a speeddetermination device 7023, a multiple-echo and bottom-echo detectiondevice 7024, a decision-making device 7025, an echo measuring device7026, as well as a self-learn device 7027.

The echo identification device 7021 examines the echo curve, which hasbeen conveyed by the echo-curve acquisition device 102, 110 for echoes205, 206, 207, 208, 209 contained in said curve. The tracking device7022 undertakes grouping of echoes from various measuring cycles in sucha manner that echoes caused by the same reflection location in thecontainer, and which echoes arise on the basis of identical signalpaths, are aggregated to form groups. On the basis of these groups,which are also referred to as “tracks” it is possible, for example, toreliably determine the speed of an echo. The speed determination device7023 determines at least one key figure relating to the speed of theechoes of the then current echo curve. The multiple-echo and bottom-echodetection device 7024 classifies multiple echoes and bottom echoes.

On the basis of the identified echoes, tracks and of the classification,undertaken according to bottom echoes and multiple echoes, theself-learn device 7027 may be in a position to automatically learn mediacharacteristics and container characteristics. On the basis of all thevalues determined so far, the decision-making device 7025 may make adecision as to which echo of the echo curve was generated by the feedmaterial reflection. With reference to the echo measuring device 7026the precise position of the echo can be determined, for example with theuse of automatically acquired characteristic values of a medium or of acontainer in the context of indirect measuring. Furthermore, influencesof an overlay medium can be compensated for.

The diagrams of FIG. 8 show a sequence of measuring cycles as they couldbe carried out with a measuring device 701 according to the invention.At consecutive points in time t₀<t₁<t₂<t₃<t₄<t₅ the container 109 to bemonitored is first filled with a medium 106 and subsequently emptiedagain. The echo curves 801, 802, 803, 804, 805, 806 acquired at therespective points in time by a fill-level measuring device 701 accordingto the invention are charted directly beside the diagram of thecontainer at the respective point in time.

Apart from the antenna echo E₁, the echo curve 801 of the emptycontainer 109 comprises 807 only an echo E₂ 808, caused by the bottom,and a further multiple echo E₃ 809 of the bottom reflection. Theseechoes are acquired by the echo identification device, wherein at thispoint in time no classification of the echoes has taken place yet. Theechoes are therefore preferably provided with different indices so thatthey can be algorithmically further processed.

On the basis of the identified echoes E₁ 807, E₂ 808 and E₃ 809, in afurther process step the tracking device 7022 attempts to place theidentified echoes in a logical context with echoes already identifiedearlier. Disclosures relating to the implementation of a tracking methodin the context of fill-level measuring technology are provided, forexample, in WO 2009/037000. The tracking device 7022 of the fill-levelmeasuring device 701 may initialize a first track T₀ 831 on the basis ofthe antenna reflection E₁.

Furthermore, a track T₃ 834 for tracing the bottom echo E₂ 808 and atrack T₄ 835 for tracing the multiple echo E₃ 809 at the point in timet=t₀ may be initialized.

At the point in time t=t₁ the container may be slightly filled. The echocurve 802 acquired by the fill-level measuring device is shown in FIG.8. The tracking unit of the fill-level measuring device 701 continuesthe already commenced tracks T₀ 831, T₃ 834 and T₄ 835 with the echoesof the then current measurement, which echoes originate from the samereflection location in the container. Furthermore, for monitoring thenewly-added fill level echo E₅ 812 a new track T₁ 832 is initialized.

In the further course of time the container is increasingly filled. Atthe point in time t=t₂ the container may thus be half full.Corresponding to the explanations provided in the context of FIG. 2, atthis state both a multiple reflection E₁₀ 816 of the feed materialsurface and a multiple reflection E₁₂ 818 of the container bottom isshown in the acquired echo curve 80. The newly added multiple reflectionfrom the feed material surface results in re-initialization of a trackT₂ 833, whereas the already existing tracks T₀ 831, T₁ 832, T₃ 834 andT₄ 835 are continued with the echoes of the correspondingly identicalreflection position in the container.

The container, which is almost entirely full of medium 106, is shown atthe point in time t=t₃.

On the basis of the very considerable loss of the measuring signals usedby the fill-level measuring device 701 within the medium 106 it may nowno longer be possible to acquire the first multiple reflection from thecontainer bottom. However, the tracking method is in a position to takeinto account the absence of this echo, for example by inserting aninvisible section 836 within the track T₄ 835. The other tracks areexpanded by the acquired echoes of the echo curve 804 according to theabove description.

During subsequent emptying of the container the first multiplereflection E₂₁ 827 of the container bottom makes a reappearance at thepoint in time t=t₄. The associated track T₄ 835 is continued again withthe multiple echo of the bottom reflection. Furthermore, the existingtracks are expanded in the known manner.

For each of the measuring cycles carried out at the points in timet₀<t₁<t₂<t₃<t₄<t₅ a track list is present in the sensor, which tracklist is provided by the tracking device 7022, and which track listdescribes the then current tracks 83 at the respective point in time.The track list may, for example, comprise vectors that in relation toeach track describe the locations of the respectively associated echo.However, it may also be possible to use a memory-optimizedrepresentation as shown, for example, in EP 2 309 235 A1. The methodproposed therein also provides an option of dividing a track, in otherwords a sequence of echoes with an identical reflection origin, intosections of time in which the associated echo comprises an almostconstant speed.

In the context of further signal processing, preferably on the basis ofthe tracks 831, 832, 833, 834, 835, an analysis for multiple echoes andbottom echoes is carried out. This may result in a classification of theacquired echoes in such a manner that the echoes of the tracks T₂ 833are multiple echoes of the respective echoes of the track T₁ 832,because track T₂ moves consistently in the same direction as track T₁.Furthermore, the multiple-echo and bottom-echo detection device 7024 mayclassify that the echoes of the track T₃ describe the bottom of thecontainer, because they move in a push-pull manner in relation to thedirection of movement of the fill level echoes of the track T₁.

Self-Learning the Permittivity Value of the Medium:

With the use of the information of an acquired fill level track T₁ 832,which groups reflections from the feed material surface, and of anassociated bottom track T₃ 834, which is classified as such, whichbottom track T₃ 834 groups reflections from the container bottom,according to the invention the self-learn device 7027 can deduce therelationship of the characteristics of the medium 106 to that of theoverlay atmosphere 107:

$\frac{ɛ_{M} \cdot \mu_{M}}{ɛ_{L} \cdot \mu_{L}} = \left( {1 + {\frac{V_{B}}{V_{L}}}} \right)^{2}$

wherein ε_(M) and ε_(L) denote the permittivity values of the medium andof the overlay atmosphere, and μ_(m) and μ_(L) denote the permeabilityvalues of the medium and of the overlay atmosphere. Furthermore, V_(B)denotes the speed of a bottom reflection or of a bottom echo, and V_(L)denotes the speed of a feed material reflection or of a feed materialecho or of a fill level echo.

The speeds of the respective echoes can be determined by means of thelocal gradient of the associated tracks T₁ 832 and T₃ (834).

As an alternative, the speed V_(E) of an echo, of a track, or of areflection can be determined, according to the following equation, froma position shift of the echo, track or the reflection between twodifferent measuring cycles of the fill-level measuring device:

$V_{E} = \frac{{D_{E}\left( t_{2} \right)} - {D_{E}\left( t_{1} \right)}}{t_{2} - t_{1}}$

wherein the following apply:

-   -   D_(E)(t₂) electrical distance to the echo, track or the        reflection in measuring cycle 2)    -   D_(E)(t₁) electrical distance to the echo, track or the        reflection in measuring cycle 1    -   t₂ point in time at which measuring cycle 2 is carried out    -   t₁ point in time at which measuring cycle 1 is carried out.

With the application of regression methods it is also possible to useseveral positions of the echoes of a track to determine the speed of anecho. However, it may also be possible to determine the speed relatingto entire sections of a track in which the speed of the echoes is almostconstant. The method described in EP 2 309 235 A1 can be used totransform a track into sections of constant speeds. Furthermore, it maybe possible to determine the speed from a Doppler analysis of theechoes.

Since in a multitude of applications the overlay atmosphere isrepresented by air, the above correlation can approximately be used fordirect acquisition of the media characteristics of the feed material:

${ɛ_{M} \cdot \mu_{M}} = \left( {1 + {\frac{V_{B}}{V_{L}}}} \right)^{2}$

At this stage it should be pointed out that in contrast to hitherto-usedmethods, no information whatsoever relating to the height of thecontainer or the length of the dome shaft is required for determiningthe media characteristics. Furthermore, the above correlations can alsobe derived by means of the speed ratios of the multiple reflections 833of the feed material and of the multiple reflections 835 of thecontainer bottom.

Self-learning the length of the dome shaft from the position of twomultiple echoes:

With the use of the position of an acquired multiple echo E_(MLN1) 207of the feed material reflection, which multiple echo E_(MLN1) 207 hasbeen classified as such and is to comprise an electrical distance ofD_(MLN1), and with the use of the position of an acquired multiple echoE_(MLN2), which multiple echo E_(MLN2) has been classified as such andcomprises an electrical distance of according to the invention theself-learn device 7027 can deduce the length d_(D) of a dome shaft 503,613:

$d_{D} = \frac{{\left( {N_{1} + 1} \right) \cdot D_{{MN}\; 2}} - {\left( {N_{2} + 1} \right) \cdot D_{{MN}\; 1}}}{\sqrt{ɛ_{L} \cdot \mu_{L}} \cdot \left( {N_{1} - N_{2}} \right)}$

wherein N₁ denotes the order of the multiple echo at the distanceD_(MN1) and N₂ denotes the order of the multiple echo at the distanceD_(MN2). If it is assumed that the feed material echo is a multiple echoof the order of 0 with an electrical distance of D_(L), then, accordingto the invention, the self-learn device 7027 can also determine thelength of the dome shaft by means of the feed material reflection inconjunction with a further multiple reflection:

$d_{D} = \frac{{\left( {N_{1} + 1} \right) \cdot D_{L}} - D_{{MN}\; 1}}{\sqrt{ɛ_{L} \cdot \mu_{L}} \cdot N_{1}}$

If it is, furthermore, assumed that air is used as the overlayatmosphere, then in good approximation √{square root over(ε_(L)·μ_(L))}=1 results, and consequently the above equations can besimplified accordingly.

Self-learning the length of the dome shaft from the intersection of atleast two speed vectors of multiple echoes:

FIG. 9 shows an example of a sequence of echoes in a fill levelmeasuring process according to the schematic of the track diagram ofFIG. 8. The fill-level measuring device may consecutively identifyvarious echoes that in the diagram may be designated ⊕. The trackingdevice 7022 groups the received echoes according to their reflectionposition. The track T_(L) 901, which groups the echoes of the feedmaterial reflection, the track T_(ML1) 902, which groups the echoes ofthe first multiple reflection from the feed material surface, and thetrack T_(ML2) 903, which represents the echoes of the second multiplereflection from the feed material surface, may be formed in this manner.

In a first advantageous process step the tracks may be converted totrack segments 904. Formation of the segments takes place in such amanner that measurements in which the echoes of a track move at(approximately) constant speed or with an identical speed vector can berepresented in a memory-optimized manner by a mathematical straight lineequation or by two supporting points 905, 906. Disclosures forimplementing this step are provided, for example, in EP 2 309 235 A1.

On the basis of the segment view of the tracks, by means of theself-learn device 7027 the fill-level measuring device can identify atleast one segment pair 907, 908 that is valid in the same time period,which segment pair 907, 908 is caused by the same reflection position inthe container, i.e. comprises a multiple-echo relationship, and which atthe same time in each case comprises a gradient that is significantlygreater than zero. The gradient of a segment may be equivalent to thespeed of the echo on which the segment is based.

The identified segment pair 907, 908 is further investigated within theself-learn device. In particular, the mathematical straight lineequations of the selected segments are determined in order to, on thebasis of these equations, calculate the intersection S of the twostraight lines according to known methods.

The distance D at which the two straight lines intersect corresponds tothe length of the dome shaft D_(D) of the container to be measured atthat time. With the use of the materials characteristics of the overlayatmosphere, the electrical length of the dome shaft D_(D) can beconverted to the physical length of the dome shaft d_(D). The followingapplies:

$d_{D} = \frac{D_{D}}{\sqrt{ɛ_{L} \cdot \mu_{L}}}$

If it is assumed that air is the overlay atmosphere, then the electricallength of the dome shaft in good approximation corresponds to thephysical length of the dome shaft.

The above representation of a preferred embodiment illustrates thefunctionality of the method by means of forming a track and tracksegments. Fundamentally, the principle of the disclosed invention canalso be implemented by means of individual echoes that have beenrecognized by a classification device as being multiple echoes. Themathematical straight line equations describe the then current speedvector of the respective echoes, and in this case are defined in thatthe straight lines must lead through the then current point of therespective echo, which point may be defined by the respective positionand the then current point in time. Furthermore, the gradient of therespective straight line is identical to the then current speed of therespective echo. The straight line equations are thus precisely definedand make it possible to achieve the mathematical calculation of theintersection S as already disclosed above.

The speed of an echo can easily be determined by means of the localgradient of the associated tracks. As an alternative, the speed can bedetermined from a position shift of the echoes of a track. By applyingregression methods it is also possible to use several positions of theechoes of a track in order to determine the speed of an echo. However,it may also be possible to determine the speed relating to entiresections of a track in which the speed of the echoes is almost constant.Furthermore, it may be possible to determine the speed from a Doppleranalysis of the echoes.

At this stage it should be pointed out that it may not matter whichmultiple echoes are used for the above-mentioned calculation. It is, inparticular, also possible to determine the intersection S by means of astraight line 907, or of a speed vector of the feed material echo and astraight line 908, or of a speed vector of a multiple reflection fromthe feed material surface. Furthermore, it may be possible to determinethe intersection S by means of a straight line 907 of a first multiplereflection of the order N1 and of a straight line 908 of a furthermultiple reflection of the order N2 from the feed material surface.Moreover, in order to improve the accuracy or for plausibility checks itmay be possible to calculate a multitude of intersections of differentmultiple reflections, and to statistically evaluate the positions of theaforesaid, for example by averaging or variance analyses.

Self-learning the container height from the intersection of at least onespeed vector of a feed material echo and of at least one speed vector ofa bottom echo:

FIG. 10 again shows an example of a sequence of echoes in a fill-levelmeasuring process according to the schematic of the track diagram ofFIG. 8. The fill-level measuring device according to the invention mayconsecutively identify various echoes that in the diagram may bedesignated ⊕. The tracking device 7022 groups the received echoesaccording to their reflection position. The track T_(L) 1001, whichgroups the echoes of the feed material reflections, and the track T_(B)1002, which represents the echoes of the reflection from the containerbottom, may be formed in this manner.

In a first advantageous processing step the tracks may be converted totrack segments 1003. Formation of the segments takes place in such amanner that measurements in which the echoes of a track move at(approximately) constant speed or with an identical speed vector can berepresented in a memory-optimized manner by a mathematical straight lineequation or by two supporting points 905, 90. Disclosures forimplementing this step are provided, for example, in EP 2 309 235 A1.

On the basis of the segment view of the tracks, by means of theself-learn device 702 a fill-level measuring device according to theinvention can identify at least one segment pair 1004, 100 that occursat the same time and that in each case comprises a significant gradientgreater than zero. Furthermore, precisely one 100 of the identifiedsegments must be caused by a reflection from the feed material surface20, and a further segment must be caused by a reflection from thecontainer bottom 20.

The identified segment pair 1004, 1005 is further investigated withinthe self-learn device. In particular, the mathematical straight lineequation of the selected segments is determined in order to, on thebasis of these equations, calculate the intersection S of the twostraight lines according to known methods.

The distance D at which the two straight lines intersect corresponds tothe height D_(B) of the container to be measured at that time. With theuse of the materials characteristics of the overlay atmosphere, theelectrical distance to the container bottom D_(E) can be converted tothe physical distance to the container bottom d_(B). The followingapplies:

$d_{B} = \frac{D_{B}}{\sqrt{ɛ_{L} \cdot \mu_{L}}}$

If it is assumed that air is the overlay atmosphere, then the electricaldistance to the container bottom in good approximation corresponds tothe physical distance to the container bottom.

The above representation of a preferred embodiment illustrates thefunctionality of the method by means of forming a track and tracksegments. Fundamentally, the principle of the disclosed invention canalso be implemented by means of individual echoes that have beenrecognized by a classification device as being a fill level echo or abottom echo. In this case the mathematical straight line equations aredefined in that the straight lines must lead through the then currentpoint of the respective echo, which point may be defined by therespective position and the then current point in time. Furthermore, thegradient of the respective straight line is identical to the thencurrent speed of the respective echo. The straight line equations arethus precisely defined and make it possible to achieve the mathematicalcalculation of the intersection S as already disclosed above.

The speed of an echo can easily be determined by means of the localgradient of the associated tracks. As an alternative, the speed can bedetermined from a position shift of two echoes of a track. By applyingregression methods it is also possible to use several positions of theechoes of a track in order to determine the speed of an echo. However,it may also be possible to determine the speed relating to entiresections of a track in which the speed of the echoes is almost constant.Furthermore, it may be possible to determine the speed from a Doppleranalysis of the echoes.

In addition, at this stage it should be pointed out that it may notmatter which pair of a feed material reflection and a bottom reflectionis used for the above-mentioned calculation.

Furthermore, it may be possible to determine the intersection S by meansof a straight line 1005, a first multiple reflection from the containerbottom, and a straight line of a further multiple reflection from thecontainer bottom, wherein the order of the multiple reflections differs.Moreover, in order to improve the accuracy or for plausibility checks itmay be possible to calculate a multitude of intersections of differentmultiple reflections from the container bottom, and to statisticallyevaluate the positions of the aforesaid, for example by averaging orvariance analyses.

Self-learning the permittivity values of several media in interfacemeasuring by means of the speeds of at least two echoes:

Fill level sensors that determine the position of a feed materialsurface according to a transit time method are increasingly also usedfor determining the position of an interface. FIG. 11 shows such anapplication case of a fill-level measuring device. The container 1101 isfilled with a lower medium 1102 to a distance d_(I), wherein thematerials characteristics of said medium 1102 may be denoted by ε_(B)and μ_(B). Furthermore, the container 1101 is filled with an uppermedium 1103 to a distance d_(L), wherein the materials characteristicsof said medium 1103 are to be characterized by ε_(I) and μ_(I). Theoverlay atmosphere 1104 may comprise the materials characteristics ε_(L)and μ_(L). Apart from the fill level echo E_(L) 1106 generated by theupper medium 1103, and the bottom echo E_(B) 1108 generated by thecontainer bottom, the echo curve 1105 acquired by the fill-levelmeasuring device comprises an interface echo Er 1107 generated by theinterface 1109, which interface echo E_(B) 1107 may comprise anelectrical distance of D_(I). According to the state of the art theechoes of each acquired echo curve are identified by the echoidentification device 7021, whereupon the tracking device 7022 may, forexample, establish three tracks. A first track T_(L) may group theechoes of the feed material surface 1110; a further track T_(I) mayrepresent the echoes of the interface 1109. Furthermore, a third trackT_(B) may be acquired which aggregates the echoes of the containerbottom.

In interface installations, multiple echoes of the feed material surfacecan be identified according to known methods. The length of the domeshaft 1111 can be determined by an analysis of two multiple reflectionsfrom the feed material surface according to the principle presentedabove. Moreover, in particular measuring situations, it is possible,when taking interface measurements, to obtain knowledge about thecharacteristics of the lower medium 1102 and about the upper medium1103.

With reference to a track diagram, FIG. 12 shows a first specialmeasuring situation that is used by the fill-level measuring device 701according to the invention, and therein in particular in the self-learndevice 7027, in order to gain knowledge about the characteristics of themedia in the container.

In the shown period of time between t=t₁₂₀ and t=t₁₂₁ the track T_(I) ofthe interface echo 1107 has (approximately) the same gradient as has thetrack T_(B) of the bottom echo 1108. In other words, in the period oftime under consideration the bottom echo and the interface echo have thesame speed. The speed of the echoes can easily be determined by means ofone of the methods described above.

From these circumstances the self-learn device 7027 concludes that thephysical distance d_(L) to the feed material surface 1110 changes atthat time, whereas the physical distance d_(I) to the interface surface1109 remains constant.

In this special situation of a stationary nature of the interface layer,the following correlation can be determined from the then current speedV_(L) of the feed material reflection 1106, 1206, from the speed of theinterface reflection 1107, 1205 and from the speed V_(B) of the bottomreflection 1108, 1204:

$\frac{ɛ_{I} \cdot \mu_{I}}{ɛ_{L} \cdot \mu_{L}} = {\left( {1 + {\frac{V_{I}}{V_{L}}}} \right)^{2} = \left( {1 + {\frac{V_{B}}{V_{L}}}} \right)^{2}}$

wherein the following apply:

-   -   ε_(I) permittivity value of the upper medium 1103    -   μ_(I) permeability value of the upper medium 1103    -   ε_(L) permittivity value of the overlay atmosphere 1104, and    -   ε_(L) permeability value of the overlay atmosphere 1104.

In the often encountered case where the overlay atmosphere consists ofair, consequently in good approximation the following applies to thecharacteristics of the upper medium 1102:

${ɛ_{I} \cdot \mu_{I}} = {\left( {1 + {\frac{V_{I}}{V_{L}}}} \right)^{2} = \left( {1 + {\frac{V_{B}}{V_{L}}}} \right)^{2}}$

On the basis of this materials characteristic it is from now on possibleto convert the electrical distance D_(I) of the interface to a physicaldistance d_(I).

The required speed values can be determined according to any of themethods described above by means of a correspondingly designed speeddetermination device 7023. Determining the speed by means of a segmentdiagram of the tracks, shown in FIG. 12, may be particularlyadvantageous.

By means of a track diagram, FIG. 13 shows a second special measuringsituation that is used by the fill-level measuring device 701 accordingto the invention, and therein in particular in the self-learn device7027, in order to gain knowledge about the characteristics of the mediain the container.

In the shown period of time between t=t₁₃₀ and t=t₁₃₁ the track T_(I) ofthe interface echo 1107 has a gradient other than 0. The track T_(B) ofthe bottom echo 1108 also comprises a gradient other than 0, whereas thetrack T_(L) of the fill level echo 1106 comprises a gradient of(approximately) 0. In other words, in the period of time underconsideration the bottom echo and the interface echo show a pronouncedmovement, i.e. their speed is greater than 0, whereas the speed of thefill level echo is 0. The speed of the echoes can easily be determinedby means of one of the methods described above.

From these circumstances the self-learn device 7027 concludes that thephysical distance d_(L) to the feed material surface 1110 does notchange at that time, whereas the physical distance d_(I) to theinterface surface 1109 is subject to changes.

In this special situation of a stationary nature of the feed materialsurface, the following correlation can be determined from the thencurrent speed V_(L) of the feed material reflection 1106, 1206, from thespeed V_(I) of the interface reflection 1107, 1205, and from the speedV_(B) of the bottom reflection 1108, 1204:

$\frac{ɛ_{B} \cdot \mu_{B}}{ɛ_{I} \cdot \mu_{I}} = \left( {1 + {\frac{V_{B}}{V_{L}}}} \right)^{2}$

wherein the following apply:

-   -   ε_(B) permittivity value of the lower medium 1102    -   μ_(B) permeability value of the lower medium 1102    -   ε_(I) permittivity value of the upper medium 1103, and    -   μ_(I) permeability value of the upper medium 1103.

If the media characteristics ε_(I)·μ_(I) of the upper medium have beendetermined in advance, then it is possible to directly deduce thematerials characteristics ε_(B)·μ_(B) of the lower medium, with suchdeduction being independent of the characteristics of the overlayatmosphere.

The required speed values can be determined according to any of themethods described above by means of a correspondingly designed speeddetermination device 7023. Determining the speed by means of a segmentdiagram of the tracks, as shown in FIG. 13, is particularlyadvantageous.

Furthermore, by means of a track diagram, FIG. 14 shows a third specialmeasuring situation that is used by the fill-level measuring device 701according to the invention, and therein in particular in the self-learndevice 7027, in order to gain knowledge about the characteristics of themedia in the container.

In the shown period of time between t=t₁₄₀ and t=t₁₄₁ the track T_(L) ofthe fill level echo 1106 has (approximately) the same gradient as hasthe track T_(I) of the interface echo 1107, wherein both tracks have agradient other than 0. The track T_(B) of the bottom echo 1108 alsocomprises a gradient other than 0. In other words, in the period of timeunder consideration the fill level echo and the interface echo show apronounced, uniform, movement at the same speed, i.e. they both move atthe same speed greater than 0. The speed of the echoes can easily bedetermined by means of one of the methods described above.

From these circumstances the self-learn device 7027 concludes that thephysical thickness of the upper medium remains constant in the period oftime under consideration:

d _(L) −d _(I)=const.

In this special situation of a constant thickness of the upper medium,the following correlation can be determined from the then current speedV_(L) of the feed material reflection 1106, 1206, from the speed V_(I)of the interface reflection 1107, 1205, and from the speed V_(B) of thebottom reflection 1108, 1204:

$\frac{ɛ_{B} \cdot \mu_{B}}{ɛ_{I} \cdot \mu_{I}} = {\left( {1 + {\frac{V_{B}}{V_{L}}}} \right)^{2} = \left( {1 + {\frac{V_{B}}{V_{I}}}} \right)^{2}}$

In the often encountered case where the overlay atmosphere consists ofair, consequently in good approximation the following applies to thecharacteristics of the upper medium 1102:

${ɛ_{B} \cdot \mu_{B}} = {\left( {1 + {\frac{V_{B}}{V_{L}}}} \right)^{2} = \left( {1 + {\frac{V_{B}}{V_{I}}}} \right)^{2}}$

On the basis of this materials characteristic it is from now onpossible, by measuring the reflection from the container bottom, toindirectly deduce the position of the feed material surface or theposition of the interface surface.

The required speed values can be determined according to any of themethods described above by means of a correspondingly designed speeddetermination device 7023. Determining the speed by means of a segmentdiagram of the tracks, as shown in FIG. 14, is particularlyadvantageous.

Self-learning the permittivity values of several media in interfacemeasuring by means of the positions and the speeds of at least twoechoes:

The hitherto disclosed methods for determining media characteristics ininterface measuring require at least one of the three constellations,described above, of the special filling or emptying of a container.Moreover, it is, however, also possible, by incorporating the positionsof the individual echoes, to derive a generally-valid correlationaccording to which the media characteristics or materialscharacteristics of the feed materials 1102, 1103 in a container can becalculated.

Starting from the circumstances as shown in FIG. 11, for interfacemeasurements the following can be derived to be universally valid fromthe physical principles of the electrical distances and the speeds ofthe acquired echoes:

${ɛ_{I} \cdot \mu_{I}} = \left( \frac{V_{L} - V_{I} + {\frac{D_{I} - D_{L}}{D_{B} - D_{I}} \cdot \left( {V_{B} - V_{I}} \right)}}{{\left( {d_{B} - \frac{D_{L}}{\sqrt{ɛ_{L} \cdot \mu_{L}}}} \right) \cdot \frac{V_{B} - V_{I}}{D_{B} - D_{I}}} + \frac{V_{L}}{\sqrt{ɛ_{L} \cdot \mu_{L}}}} \right)^{2}$

and furthermore:

${ɛ_{B} \cdot \mu_{B}} = \left( \frac{D_{B} - D_{I}}{\left( {d_{B} - \frac{D_{I}}{\sqrt{ɛ_{I} \cdot \mu_{I}}}} \right) + {\frac{\sqrt{ɛ_{L} \cdot \mu_{L}} - \sqrt{ɛ_{I} \cdot \mu_{I}}}{\sqrt{ɛ_{L} \cdot \mu_{L} \cdot ɛ_{I} \cdot \mu_{I}}} \cdot D_{L}}} \right)^{2}$

wherein the following apply:

-   -   ε_(B) permittivity value of the lower medium 1102    -   μ_(B) permeability value of the lower medium 1102    -   ε_(I) permittivity value of the upper medium 1103    -   μ_(I) permeability value of the upper medium 1103    -   ε_(L) permittivity value of the overlay atmosphere 1104    -   μ_(L) permeability value of the overlay atmosphere 1104    -   D_(B) electrical distance to the echo E_(B) 1108 of the        container bottom    -   D_(I) electrical distance to the echo E_(I) 1107 of the        interface 1109    -   D_(L) electrical distance to the echo E_(L) 1106 of the surface        1110    -   V_(B) speed of the echo E_(B) 1108 of the container bottom    -   V_(I) speed of the echo E_(I) 1107 of the interface 1109    -   V_(L) speed of the echo E_(L) 1106 of the surface 1110, and    -   d_(B) distance from the fill-level measuring device to the        container bottom.

The distance d_(B) from the fill-level measuring device to the containerbottom can be entered in the context of initial operation, for exampleby the customer, and is thus known. Furthermore, in the case of devicesoperating according to the principle of the guided microwave, thisdistance corresponds to the length of the cord or of the probe alongwhich the microwaves are guided to the medium, and for this reason thevalue can already be preset in the factory. Moreover, in a multitude ofapplications, air is used as the overlay atmosphere, which results in√{square root over (ε_(L)·μ_(L))} in the above equations being able tobe replaced in good approximation by the value of 1.

The required speed values can be determined according to any of themethods described above by means of a correspondingly designed speeddetermination device 702. Determining the speed by means of a segmentdiagram of the tracks, as shown in FIG. 14, is particularlyadvantageous.

With the use of the above equations it is, for the first time, possiblealso in interface equipment to automatically acquire the permittivityvalues and the permeability values of the media contained in thecontainer by means of a single transit time measurement. From now on thevalues can be used for converting the electrical distances to theassociated physical distances. Furthermore, indirect measurement of thefill level is possible with a knowledge of the materialscharacteristics.

In the present invention different methods for determining containercharacteristics and/or media characteristics with the use of afill-level measuring device according to the invention are presented.Many methods share the common feature of classification or evaluation ofechoes as multiple echoes or bottom echoes having to be carried out inadvance. After this classification has been carried out, predominantlywith the use of the speeds of individual echoes or a group of echoes,characteristic values of the container and/or of the media containedtherein can be derived. In this context it is possible for thedetermination of the speed of an echo to take place in various ways, inparticular according to the methods described in this disclosure.

Furthermore, it should be noted that the present technical teaching isequally suited to fill level measuring according to the FMCW principleas it is to fill level measuring according to the principle of theguided microwave, the ultrasound principle, the laser principle, or anyother transit time method.

In the present description it is assumed that the analysis of the mediacharacteristics can only provide the product of the permeability valueand of the permittivity value of the medium in question. Since for themajority of media in good approximation the permeability value can beset to one, all the methods described can in good approximation also beused for directly acquiring the permittivity value of a medium.

Furthermore, determining the length of the dome shaft and of thecontainer height is described. At this stage it should be pointed outthat within signal processing of the sensor, both values can be slightlydifferent from the physical values that can be checked by measuring. Forone thing the zero point of the sensor can be changed byparameterization. Furthermore, for example, the height of a container inone application including a dome shaft installed thereon can be defined,while in other applications, for example in the case of a negativelength of the dome shaft, this definition may not make sense in thismanner. Thus, in the context of the present invention, numeric valuesshould be defined that have some relationship with the physical values,and by means of which numerical values special methods, in particularindirect measuring of the feed material layer, can be implemented.

In addition, it should be pointed out that “comprising” does not excludeother elements or steps, and “a” or “one” does not exclude a pluralnumber. Furthermore, it should be pointed out that characteristics orsteps which have been described with reference to one of the aboveexemplary embodiments can also be used in combination with othercharacteristics or steps of other exemplary embodiments described above.Reference characters in the claims are not to be interpreted aslimitations.

1. A fill-level measuring device for determining a position of a filllevel of at least one of (a) a feed material and (b) an interfacebetween two feed materials in a container emits electromagnetic oracoustic waves in a direction of a feed material surface, comprising: anecho-curve acquisition device acquiring at least one echo curve; an echoidentification device evaluating the at least one echo curve; amultiple-echo detection device classifying at least one echo of amultiple reflection from at least one of (a) a feed material surface and(b) a container bottom as a multiple echo; and a self-learn deviceautomatically determining a length of a dome shaft of a dome arranged inan apex region of the container with the use of the multiple echoclassified by the multiple-echo detection device.
 2. The fill-levelmeasuring device of claim 1, further comprising: a positiondetermination device; wherein the echo identification device identifiesseveral echoes in the echo curve; wherein the multiple-echo detectiondevice classifies at least two of the several echoes as multiple echoes;wherein the position determination device determines positions of the atleast two multiple echoes; and wherein the self-learn device uses thepositions of the at least two multiple echoes for determining the lengthof the dome shaft.
 3. The fill-level measuring device of claim 2,wherein the self-learn device uses the orders of the at least twomultiple echoes for determining the length of the dome shaft.
 4. Thefill-level measuring device of claim 1, wherein the echo identificationdevice identifies several echoes in the echo curve; wherein themultiple-echo detection device classifies two of the several echoes asmultiple echoes; wherein the fill level measuring device furthercomprising: a speed determination device determining at least two speedvectors of the at least two multiple echoes; and wherein the self-learndevice determines an intersection of at least two speed vectors of theat least two multiple echoes for determining the length of the domeshaft.
 5. A method for determining a position of a fill level of atleast one of (a) a feed material and (b) an interface between two feedmaterials, comprising the steps of: emitting electromagnetic or acousticwaves in a direction of a feed material surface; acquiring at least oneecho curve; evaluating the at least one echo curve; classifying at leastone echo of a multiple reflection from at least one of (a) the feedmaterial surface and (b) a container bottom of the container as amultiple echo; wherein automatically determining a length of a domeshaft of a dome arranged in an apex region of the container with the useof the multiple echoes classified by the multiple-echo detection device.6. A program element which, when executed on a processor of a fill-levelmeasuring device, instructs the processor to carry out the followingsteps: emitting electromagnetic or acoustic waves in a direction of afeed material surface; acquiring at least one echo curve; evaluating theat least one echo curve; classifying at least one echo of a multiplereflection from at least one of (a) the feed material surface and (b) acontainer bottom of the container as a multiple echo; whereinautomatically determining a length of a dome shaft of a dome arranged inan apex region of the container with the use of the multiple echoesclassified by the multiple-echo detection device.
 7. A computer-readablemedium for storing a program element which, when executed on a processorof a fill-level measuring device, instructs the processor to carry outthe following steps: emitting electromagnetic or acoustic waves in adirection of a feed material surface; acquiring at least one echo curve;evaluating the at least one echo curve; classifying at least one echo ofa multiple reflection from at least one of (a) the feed material surfaceand (b) a container bottom of the container as a multiple echo; whereinautomatically determining a length of a dome shaft of a dome arranged inan apex region of the container with the use of the multiple echoesclassified by the multiple-echo detection device.